JP2003344894A - Photometry device for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photometry device for a camera capable of accurately metering under an artificial light source such as a fluorescent lamp without increasing a release time lag. <P>SOLUTION: As for the camera provided with a photometry means 101 for measuring the luminance of an object in a photographing screen and a range finding means 102 for finding several ranges including a center part in the photographing screen and detecting a main object based on the outputs of image sensors 132a and 132b for photoelectrically converting the object image formed by light receiving lenses 131a and 131b and then outputting the object image as image data, in the case of metering by the range finding means 102, a timing of metering by the range finding means 102 is decided based on the photometry result of the photometry means 101. Then, the accurate photometry value can be obtained with a single measurement by the range finding means 102 even under the illumination of artificial flickering light. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric device for controlling the exposure of a camera.

[0002]

2. Description of the Related Art Conventionally, as a method for reducing a photometric error due to the influence of an AC component of an artificial light source such as a fluorescent lamp in a photometric device for controlling the exposure of a camera, Japanese Patent Application Laid-Open No. 62-259022 discloses. As disclosed,
A method of averaging photometric values by a plurality of integration operations is known.

[0003]

However, not only the photometric value of a normal photometric sensor but also the photometric value of a distance measuring sensor which is a sensor array composed of a plurality of photodiodes is used for performing spot photometry or the like. In order to improve the photometric accuracy, the photometric device of the camera responds more than the photometric sensor in the case of the photometric sensor by performing multiple photometric measurements not only when the photometric sensor is used, but also when the photometric sensor is used. There is a problem that the release time lag increases because of poor performance.

In view of the above circumstances, it is an object of the present invention to provide a photometric device for a camera capable of performing correct photometry even under an artificial light source such as a fluorescent lamp without increasing the release time lag. is there.

[0005]

SUMMARY OF THE INVENTION The present invention provides a photometric means for measuring the brightness of a subject within a photographic screen and an output of an image sensor for photoelectrically converting the subject image formed by a light receiving lens and outputting it as image data. On the basis of the above, in a camera having a distance measuring means for measuring the distance to a plurality of areas including the central portion in the image pickup screen and detecting the main subject, when the light measuring is performed by the distance measuring means, the result of the light measuring by the light measuring means is Based on the above, the timing for performing photometry by the distance measuring means is determined.

In the prior art, when the photometry is performed by the distance measuring means, the release time lag increases if the detection is performed a plurality of times like the exposure photometric means. The timing when the photometry is performed by the distance measuring means is determined based on this. By properly determining this timing, an accurate photometric value can be obtained by one photometry when the photometry is performed by the distance measuring means. It will be possible.

It is preferable that the photometry is performed a plurality of times at a predetermined cycle, and the distance measurement is performed at a timing when the subject brightness is an average value of a plurality of photometry results.

Alternatively, it is preferable that the photometric means performs the photometry a plurality of times in a predetermined cycle, and the timing for the photometry by the distance measuring means is determined based on the predetermined photometry cycle and the plurality of photometric results.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. 1 is a block diagram showing a configuration of a main part of a camera according to an embodiment of the present invention, and FIGS. 2 and 3 are photometric means 101 and distance measuring means 102 in FIG. 1, respectively.
Shows the configuration of.

The main part of the camera shown in FIG. 1 includes a photometric means 101 for measuring the subject brightness information in the photographing screen, a distance measuring means 102 for measuring the subject distance information in the photographing screen, and distance measuring information. A lens driving means 103 for driving a focus adjusting lens and a shutter means 104 for exposing the film.
And a film feeding means 105 for winding and rewinding the film, a strobe 106 for illuminating a subject by emitting light at low brightness or backlight, and a focal length detecting means for detecting focal length information of the photographing lens. 107 and a non-volatile memory 108 such as an EEPROM for storing various setting values and adjustment values
And a CPU 109 as an arithmetic control unit for controlling the sequence of the entire camera and performing an arithmetic operation, and a fast release switch for instructing the camera to perform measurement and arithmetic operation of subject information necessary for photographing such as distance measurement and photometry. 1R switch) 110, a second release switch (hereinafter, 2R switch) 111 for instructing the camera to execute shooting based on the subject information measured and calculated by turning on the 1R switch 110, and the CPU 109 Is provided in the photometric means 101
Brightness determination means for determining whether or not the shooting scene has high brightness based on the average brightness in the shooting screen measured by
112, and an exposure control unit 113 provided in the CPU 109, which controls the shutter unit 104 and the strobe 106 to perform exposure based on the luminance information selected by the luminance determination unit 112 and the information on whether or not the strobe 106 emits light. , A time measuring means 114 provided in the CPU 109 for detecting the timing of photometry by the distance measuring means 102.

The photometric means 101 shown in FIG. 2 is a photometric lens 121 for guiding the light component in the photographic screen to the photometric sensor 122, and a photometric sensor for measuring the subject brightness in the photographic screen guided by the photometric lens 121. 122, a photometric integration control means 123 for controlling the integration operation of the photometric sensor 122, and an A / D conversion means 124 for A / D converting the integrated output of the photometric sensor 122. There is. The light component of the subject guided by the photometric lens 121 is detected by the photometric sensor 122, and the detection output is A / D converted and output to the CPU 109 as photometric data.

The distance measuring means 102 shown in FIG. 3 includes a pair of light receiving lenses 131a and 131b for forming a subject image on the line sensors 132a and 132b, and a subject image formed by the light receiving lenses 131a and 131b. A pair of line sensors 132a, 132b for photoelectrically converting the light into an electric signal, distance measuring integral control means 133 for controlling the integral operation of the line sensors 132a, 132b, and the line sensor. A / D conversion means 134 as a reading means for reading subject image signals from 132a and 132b and performing A / D conversion. Two object images formed by the pair of light receiving lenses 131a and 131b are detected by the pair of line sensors 132a and 132b as distance measuring sensors, and the two image outputs are A / D converted to obtain the object. The above CP as image data
Output to U109.

Next, the operation of the camera configured as described above at the time of shooting will be described with reference to FIG. FIG. 4 is a flowchart showing the release sequence of the camera.

First, when the power switch of a camera (not shown) is turned on, data such as various setting values and adjustment values are EEP.
Read from the non-volatile memory 108 such as ROM, CPU109
Is expanded in the RAM (step S101).

It is determined whether or not the power switch of the camera (not shown) is off. If it is off, the release sequence is terminated, and if it is on, the process proceeds to step S103 (step S10).
2).

In step S103, it is determined whether or not the 1R switch 110 is on. If it is on, the process proceeds to step S104, and if it is off, the process returns to step S102.

Then, in step S104, the photometry means 101 performs photometry a plurality of times, the average value thereof is taken as the subject brightness, and the distance measurement means 102 calculates the timing of photometry.

Next, the distance measuring means 102 obtained in step S104
The photometric timing by is adjusted by the timing by the timing means 114 (step S105).

Further, in step S106, the distance measuring means 1
Photometry is performed with 02 to obtain the subject brightness near the center of the shooting screen.

Then, in step S107, distance measurement is performed, and based on the distance measurement data of each of the plurality of distance measurement areas in the photographing screen, the main subject is detected by a method such as closest selection, and subject distance data is obtained. .

Next, on the basis of the brightness information measured in steps S104 and S106, backlight control, exposure calculation, etc. are performed to calculate exposure control data (step S108).

In step S109, the amount of extension of the focus adjustment lens (not shown) is calculated based on the subject distance data obtained in step S107.

Then, in step S110, it is determined whether or not the 1R switch 110 is on. If it is on, the process proceeds to step S111, and if it is off, the process returns to step S102.

In step S111, the 2R switch 1
It is determined whether 11 is on, and if it is on, step S112.
If it is off, the process returns to step S110.

In step S112, the lens driving means 103 extends a focus adjusting lens (not shown) in accordance with the amount of extension calculated in step S109.

Next, the shutter means 104 performs exposure according to the exposure control data obtained in step S108 (step S113).

Then, in step S114, the film feeding means 105 winds the film by one frame, and the process returns to step S102.

In the above step S104 of the present embodiment, the photometric means 101 performs photometry a plurality of times in a predetermined cycle,
The lighting period T of the artificial light source and the amplitude ΔBV of the AC component are estimated, and the distance measuring means 102 is calculated using the lighting period T and the amplitude ΔBV.
Determines the timing for photometry in.

This will be described with reference to FIG.
FIG. 5 is a waveform diagram for explaining the method of determining the timing when performing photometry by the distance measuring device based on the photometric result of the photometric device and the waveform diagram for explaining the photometry by the distance measuring device. Reference numeral 141 is an artificial light source such as a fluorescent lamp. Lighting cycle of pulsating light from the light source (for example, 20 ms)
3 shows a waveform of subject brightness that fluctuates due to.

For example, the lighting frequency of the artificial light source is 50 Hz.
Assuming that, the photometric means 101 performs photometry twice at 20 ms intervals to obtain photometric values BVAE1 and BVAE2, and BVAE1-B
If VAE2≈0, the lighting cycle is 20 ms (50 Hz),
If BVAE1−BVAE2 ≠ 0, the lighting cycle is 16.7 ms.
The lighting cycle T is estimated as (60 Hz).

The amplitude ΔBV is 1 / the estimated lighting cycle T.
As shown in FIG. 5, the photometric means 101 performs photometry four times in four cycles to obtain photometric values BVAE1 to BVAE4, and an average value BVAV.
After calculating E, ΔBV is obtained by the procedure of equations (1) to (7).

ΔBVAE1 = BVAE1−BVAVE (1) ΔBVAE2 = BVAE2−BVAVE (2) ΔBVAE1 = ΔBVsinωt1 (3) ΔBVAE2 = ΔBVsin (ωt1 + π / 2) = ΔBVcosωt1 (4) [4] ω is the angular frequency (= 2π / T), and t1 is the measurement timing of BVA E1]. Therefore, dividing equation (3) by equation (4) gives ΔBVAE1 / ΔBVAE2 = sinωt1 / cosωt1 = tanωt1 (5) Therefore, ωt1 is ωt1 = tan ⁻¹ (ΔBVAE1 / ΔBVAE2) …… (6) From formulas (3) and (6), ΔBV = ΔBVAE1 / sin {tan ⁻¹ (ΔBVAE1 / ΔBVAE2)} …… (7) Then, the amplitude ΔBV can be obtained from the equation (7).

Next, using the estimated lighting period T of the artificial light source and the amplitude BV of the AC component, the timing for performing photometry by the distance measuring means 102 is obtained. Since the photometric value BVAE is BVAE = ΔBVsinωt + BVAVE (8), t0 in FIG. 5 is t0 = (T / 2π) sin ⁻¹ {(ΔBVAE4−BVAVE) / ΔBV} from equation (8). The timing at which the photometric value BVAE becomes the average value BVAVE is obtained by (9), and t0 + t = nT / 2 (10) (n is an arbitrary integer), so that t = nT / 2-t0 (11) It's time. Therefore, at the time of the fourth light measurement by the light measurement means 101, the time measurement means 114 starts the time measurement, and the distance measurement means 102 performs the light measurement at the timing of t obtained from the equation (11).

The average value B of the photometric values BVA E1 to BVA E4
VAVE is used as a photometric value by the photometric means 101.

As described above, according to the embodiment of the present invention, when the photometry is performed by the distance measuring means 102, the result of the photometry by the photometric means 101 indicates that the subject brightness which fluctuates in a predetermined cycle due to the influence of the AC component of the artificial light source. Since photometry is performed by the distance measuring means 102 at the timing when the average brightness is obtained, an accurate photometric value can be measured with one measurement by the distance measuring means 102 even under an artificial light source. Therefore, it is possible to solve the conventional problem that the release time lag is increased by a plurality of integration operations by the distance measuring means.

[0036]

As described above, according to the present invention, it is possible to realize a photometric device for a camera which can perform correct photometry even under an artificial light source without increasing the release time lag.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a camera according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of photometric means in FIG.

FIG. 3 is a block diagram showing a configuration of distance measuring means in FIG.

4 is a flowchart showing a release sequence of the camera of the embodiment shown in FIG.

FIG. 5 is a waveform chart of pulsating flow light for explaining a method of determining a timing for performing photometry by the distance measuring means based on the result of photometry of the light measuring means and the photometry by the distance measuring means in steps S104 to S106 of FIG.

[Explanation of symbols]

101 ... Photometric means 102 ... Distance measuring means 109 ... CPU (arithmetic control means) 110 ... First release switch 111 ... Second release switch 112 ... Luminance determining means 113 ... Exposure control means 114 ... Timing means

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Claims (3)

[Claims] 1. A center in an image pickup screen based on an output of a photometric unit for measuring the subject brightness in the image pickup screen and an image sensor for photoelectrically converting an object image formed by a light receiving lens and outputting it as image data. In a camera having a distance measuring means for measuring the distance to a plurality of areas including a part and detecting a main subject, when the light measuring is performed by the distance measuring means, the distance measuring means calculates the distance based on the result of the light measuring by the light measuring means. A photometric device for a camera, which determines the timing of photometry. 2. The light measuring means performs the light measurement a plurality of times at a predetermined cycle, and the distance measuring means performs the light measurement at the timing when the subject brightness is an average value of the plurality of light measurement results. Photometric device for the described camera. 3. The photometric means performs the photometry a plurality of times at a predetermined cycle, and the distance measuring means determines the timing at which the photometry is performed based on the predetermined photometry cycle and the plurality of photometric results. 1. A photometric device for the camera according to 1.